This invention relates to a method and apparatus for substantially eliminating yarn breakage in ring spinning machines upon resumption of spinning after bobbin exchange. The invention pertains in particular to those ring spinning machines which are equipped with an automatic doffing device and in which the control of the ring rail motion is effected by means of a lifter arm which is moved up and down by means of a rotating, usually heart-shaped cam disc connected to the lifter arm. The automatic doffing device is conventionally mounted on the ring spinning machine for mechanically removing the completed yarn package and subsequently inserting an empty bobbin on the spindle.
In ring spinning, after completion of a cop (yarn package), the yarn is conventionally guided by the ring rail to a location underneath the cop to apply a few yarn turns to the underwinding (or waste) spool forming part of the spindle. The result of this step is that the yarn course is not disturbed as the cop is removed, that is, the yarn remains in the guide wire, in the traveler and on the underwinding spool. Thus, when the cop is removed, the yarn is to break between the cop and the underwinding spool. For resuming the spinning operation, a new bobbin is inserted on the empty spindle after removal of the cop and the ring spinning machine is restarted, the ring rail is lifted from the underwinding position and thus the yarn is guided onto the new bobbin.
When practicing the above-outlined process, it often occurs, however, that the loose end of the yarn falls over the positioned yarn in the underwinding position of the ring rail. Further, when the ring spinning machine is stopped, as a result of the slackening of the positioned yarn, often loops are formed which may also appear upstream of the traveler when the ring rail is in the underwinding position. When the spinning operation is resumed, these loops, as well as the overhanging loose yarn end, have to be drawn through the traveler. This, in general, leads to yarn breakage, since the ring rail -- the motion of which is controlled by the eccentric, heart-shaped cam disc -- is lifted only slightly as the cam disc is set in motion.